1. Field of the Invention
The present invention relates to a magnetic disc apparatus, a magnetic head, and a production method thereof and in particular, to a magnetic head in which a recording/reproduction element is mounted on a magnetic head slider via a piezoelectric element so that the position of the recording/reproduction element can be adjusted in job mode by displacement of the piezoelectric element, and its production method, and to a magnetic disc apparatus using the magnetic head, and its production method.
2. Description of the Related Art
In a magnetic disc apparatus, recording density can be increased by increasing the recording density (linear recording density) of the magnetic disc rotation direction and the recording density (track density) of the magnetic disc radial direction.
In order to increase linear recording density, it is necessary to reduce the spacing between the magnetic head recording/reproduction element and the magnetic disc. In a conventional magnetic disc apparatus using a float type slider, spacing is reduced by weakening the floating power of the float type slider.
FIG. 10 is a perspective view of a conventional magnetic head (conventional float type magnetic head) using a float type slider. FIG. 10 shows the magnetic head with its float surface (to face a magnetic disc) upward. The reference symbol 20 denotes a slider, 13 denotes a float plane, and 21 denotes a recording/reproduction element.
When floating power of a float type slider is weakened, spacing can follow a greater waviness of the magnetic disc. However, when floating power is weakened, spacing cannot follow a surface configuration (wavelength from micrometers to millimeters, and frequency from several tens of kHz to several hundreds of kHz) of a dimension similar to that of the magnetic head slider. Accordingly, the spacing fluctuates. Moreover, the magnetic head may be brought into contact with the magnetic disc, causing friction.
Moreover, in a conventional magnetic disc apparatus, in order to increase track density, for example, a rotary actuator is used to perform track positioning by driving a head gimbal assembly consisting of a support spring and a magnetic head slider, in a magnetic disc radial direction.
However, in the case of a head gimbal assembly, the magnetic head position is to be controlled via a structure of a low rigidity and low resonance frequency such as a gimbal spring from a position far away from the magnetic head. Accordingly, it is difficult to perform track positioning with high speed and high accuracy.
Moreover, in the case of a recording/reproduction element in contact with a magnetic disc, the magnetic head is moved against friction between the recording/reproduction element and the magnetic disc. Accordingly, it becomes more difficult to perform track positioning with high accuracy.
Thus, in the conventional magnetic disc apparatus, it has been difficult to simultaneously improve linear recording density and track density. For improving recording density, various suggestions have been made. Firstly, conventional techniques for improving linear recording density will be shown.
Tribology and Mechanics of Magnetic Storage System, Volume 7, 1990, pp 158-164 [1] discloses a technique for reducing spacing by burying a piezoelectric element expanding and contracting in parallel to the drive electric field, into the back of a float type magnetic head slider and applying an electric field to this piezoelectric element.
FIG. 11 is a perspective view of a conventional magnetic head (magnetic head slider) in which a piezoelectric element is buried into the back of a float type magnetic head slider. FIG. 12 explains the operation of a conventional magnetic head (magnetic head slider) in which a piezoelectric element is buried into the back of a float type magnetic head slider. In FIG. 11, the reference symbol 20 denotes a slider, 21 denotes a recording/reproduction element, 22 denotes a layered piezoelectric element, and 23 denotes electrodes. In FIG. 12, the reference symbol 30 denotes a magnetic disc. The reference symbol 24a indicates a displacement direction of the piezoelectric element, 24b indicates a displacement direction of the recording/reproduction element caused by the displacement of the piezoelectric element, and 17 indicates the spacing direction.
Japanese Patent Publication 1-107385 [2] discloses a magnetic recording apparatus in which a displacement sensor measures the distance between a magnetic recording medium and a magnetic head and an actuator is driven so as to maintain the distance constant, so that the interval between the medium and the head is reduced. This magnetic recording apparatus is constituted as follows. The interval between the magnetic recording medium and the magnetic head is measured by an intensity change of the return light emitted from a light reflection intensity type displacement meter through an optical fiber and reflected from the medium surface. The magnetic head uses a piezoelectric actuator driven by a servo circuit and an amplifier according to a displacement fluctuation signal from the light reflection intensity type displacement meter, and maintains a constant distance from the surface of the magnetic recording medium. Thus, by measuring the distance between the magnetic recording medium and the magnetic head using a displacement sensor so that the distance is maintained constant by driving the actuator attached to the magnetic head, it is possible to maintain a very small interval between the magnetic recording medium and the magnetic head as a non-contact state or contact state with a very small weight.
Japanese Patent Publication 7-235157 [3] discloses a magnetic disc apparatus in which the distance between the magnetic head and the magnetic disc is measured from time to time and maintained constant while performing a signal recording/reproduction so that a floating margin is reduced and recording is enabled with a smaller floating amount. This magnetic disc apparatus is constituted as follows. When the magnetic disc apparatus is started and the magnetic disc is rotated at a comparatively low speed, the magnetic head floats over the magnetic disc surface and reads a signal recorded, with the reproduction element mounted, while traveling in a floating state. From strength of this signal, a detailed floating amount fluctuation is read and a control signal is transmitted to the piezoelectric element. The piezoelectric element, upon reception of the control signal, expands and contracts in the longitudinal direction so as to raise and lower the recording element and the reproduction element according to the unevenness of the surface so as to maintain a predetermined distance from the surface and maintain a float amount constant. Accordingly, it is possible to obtain a magnetic disc apparatus having a smaller float amount and a higher recording density. Moreover, it is possible to prevent contact between the magnetic head and the magnetic disc.
Next, conventional techniques for improving mainly the track density will be shown.
Although the document name [4] is unknown, there has been suggested a technique to drive a support spring supporting a magnetic head slider by an electromagnetic actuator in order to increase track density.
The Japan Society of Mechanical Engineers, proceedings (4), No. 98-1, 1998, pp 208-209 [5] describes a technique to drive an entire magnetic head slider by a piezoelectric element beam.
The Japan Society of Mechanical Engineers, proceedings (4), No. 98-1, 1998, pp 210-211 [6] describes a technique to drive a recording/reproduction element by an electrostatic actuator provided at the back end of a slider.
Japanese Patent Publication 3-245315 [7] discloses a head slider on which a drive member is provided for changing the position of a transducer in the positioning direction (track width direction), so as to perform positioning with high speed and high accuracy. This head slider is constituted as follows. The drive member is a piezoelectric element which changes its size in a direction perpendicular to the positioning direction. Furthermore, a conversion mechanism is provided on the slider for converting the piezoelectric element size change into a displacement amount of the transducer in the positioning direction. The conversion mechanism converts a deformation amount of the drive member in a direction perpendicular to the positioning direction of the transducer (track width direction) into a displacement amount in the positioning direction of the transducer. Thus, use of the drive member increases the degree of freedom.
Japanese Patent Publication 6-176336 [8] discloses a magnetic recording/reproduction apparatus in which data parallel transfer is enabled, high speed data transfer is realized, and a servo can be operated for each of the recording/reproduction elements, increasing positioning accuracy and track density. This magnetic recording/reproduction apparatus is constituted as follows. Rail members constituting the slider are connected to a piezoelectric element and the rail interval is made variable. By using a plurality of these configurations, a multi-element slider is realized. In this apparatus, for each of the recording/reproduction elements, there is provided a recording/reproduction circuit, so that recording/reproduction is performed simultaneously. By controlling the piezoelectric element for the rail interval, it is possible to accommodate variable track densities.
Japanese Patent Publication 7-73619 [9] discloses a magnetic head and a magnetic recording/reproduction apparatus which performs tracking control of the magnetic head. The magnetic head is intended for enlarging a data region in a recording medium and increasing accuracy of off track control. This magnetic head and the magnetic recording/reproduction apparatus using this magnetic head are constituted as follows. A magnetic head is constituted by providing a piezoelectric element at a cut-off portion of a slider for moving a movable block having a thin film head in the magnetic disc radial direction by electrostrictive displacement. The piezoelectric element is driven according to read data error detection so as to control the off track. Thus, servo information can be removed from a data region of the recording medium.
FIG. 11 shows a magnetic head in which a piezoelectric element expanding and contracting in parallel to the drive electric field is buried in the back of a floating type magnetic head slider. By applying an electric field to this piezoelectric element, spacing is reduced. With this magnetic head, as shown in FIG. 12, the recording/reproduction element may be inclined and the recording/reproduction element may not be at the lower most point of the magnetic head slider. In other words, there may arise a clearance between the recording/reproduction element and a magnetic disc. Moreover, in this technique, the piezoelectric element expands and contracts too much in the magnetic disc rotation direction and time fluctuation (jitter) of a recording/reproduction signal may become remarkable.
The technique described in Document [2], i.e., the technique to drive a magnetic head into the spacing direction by a piezoelectric actuator has a problem that it is difficult to follow the magnetic disc swell (amplitude of 1 to 10 micrometers, wavelength of several tens to hundreds of mm, and frequency of several tens to hundreds of Hz) only by the piezoelectric actuator.
The magnetic head used in the magnetic disc apparatus described in Document [3] has a structure that a recording/reproduction element is attached downward via a piezoelectric element at the rear portion of the magnetic head slider. Accordingly, a piezoelectric element and a recording/reproduction element are mounted on each magnetic head slider, which is not appropriate for mass production of magnetic heads.
The technique to drive the support spring supporting a magnetic head slider, by an electromagnetic actuator, and the technique to drive the entire magnetic head slider by a piezoelectric element beam have a problem that resonance frequency is too low. Moreover, since the drive source is apart from the recording/reproduction element, there is a problem that there arises a delay of a reproduction signal used for position detection information.
The technique to drive a recording/reproduction element by an electrostatic actuator provided at the rear end of the slider has a problem that a flexible spring structure is used and resonance frequency is too low, and because the drive force is small, it is difficult to drive the recording/reproduction element at a high speed.
The head slider described in Document [7] can perform positioning in the track direction but cannot control the spacing direction.
The magnetic recording/reproduction apparatus described in Document [8] can perform a multi-element simultaneous tracking but cannot perform control in the spacing direction.
The magnetic head described in Document [9] has a structure that a thin film head is attached via a piezoelectric element at a cut-off portion formed in the slider. Accordingly, it is necessary to mount a piezoelectric element and a recording/reproduction element for each slider, which is not appropriate for mass production of magnetic heads.
Moreover, the minimum spacing is the state that a recording/reproduction element of the magnetic head is in contact with the surface of a magnetic disc. However, with the conventional techniques, it is difficult to increase the track positioning accuracy in such a minimum spacing state.
It is therefore an object of the present invention to provide a magnetic head capable of following swell of the roughness of a magnetic disc with small spacing so as to increase linear recording density. Another object of the present invention is to provide a magnetic head capable of positioning with high accuracy in the magnetic disc radial direction, thereby increasing track density. Furthermore, it is an object of the present invention to provide a magnetic head having small spacing and capable of positioning with high accuracy in the magnetic disc radial direction, thereby simultaneously increasing linear recording density and track density. Moreover, the present invention provides a magnetic head production method appropriate for mass production of magnetic heads and provides a magnetic disc apparatus using magnetic heads.
The magnetic disc apparatus in one embodiment of the invention comprises a magnetic head slider floating on air with respect to a predetermined magnetic disc, the magnetic head slider including: a recording/reproduction element in the vicinity of an air flow out end of the magnetic head slider; and a piezoelectric element for displacing the recording/reproduction element in the direction toward the magnetic disc. The piezoelectric element is displaced in a direction perpendicular to the voltage application direction utilizing, for example, a slide vibration.
In this magnetic disc apparatus, the recording/reproduction element is mounted on the magnetic head slider via a piezoelectric element. Accordingly, by controlling the voltage applied to the piezoelectric element so as to control the displacement amount of the piezoelectric element, it is possible to displace the recording/reproduction element. Thus, by using a piezoelectric element, it is possible to control the position of the recording/reproduction element with high rigidity, high speed, and high accuracy.
By using a piezoelectric element displaced in the spacing direction by a voltage application, it is possible to control spacing between the recording/reproduction element and the magnetic disc. By controlling the displacement amount of the piezoelectric element so that the recording/reproduction element is in slight contact with the surface of the magnetic disc, it is possible to maintain minimum spacing. Since the piezoelectric element is used, it is possible to obtain spacing control with high rigidity, high speed, and high accuracy.
By using a piezoelectric element displaced in a radial direction (track direction) of a magnetic disc, it is possible to control the position of the recording/reproduction element in the track direction. Since a piezoelectric element is used, it is possible to perform track positioning control with high rigidity, high speed, and high accuracy.
By using a layered configuration of a piezoelectric element displaced in a spacing direction and a piezoelectric element deflecting in a track direction, it is possible to displace the recording/reproduction element in two directions. This permits control of the spacing between the recording/reproduction element and the magnetic disc, and the track positioning with high rigidity, high speed, and high accuracy. That is, it is possible to simultaneously perform spacing control and track positioning control without interfering with each other.
In another embodiment of the invention, the magnetic disc apparatus uses a magnetic disc slider including a recording/reproduction element arranged in the vicinity of an air flow out end of a magnetic head slider floating on air, and formed on a piezoelectric element deflecting in parallel to the voltage application direction and on a piezoelectric element deflecting in a direction perpendicular to the voltage application direction.
In this latter embodiment, the recording/reproduction element is mounted via two piezoelectric elements displaced in different directions and accordingly, it is possible to control the position of the recording/reproduction element in two directions. Since a piezoelectric element is used, it is possible to control the position of the recording/reproduction element with high rigidity, high speed, and high accuracy. It is possible to control the position in two directions without interfering with each other. It is possible to perform position control simultaneously in two directions.
By providing a piezoelectric element displaced in the rotation direction of a magnetic disc and a piezoelectric element displaced in the spacing direction, it is possible to control the position of the recording/reproduction element in the disc rotation direction and the spacing direction. The control of the position of the recording/reproduction element in the disc rotation direction can reduce recording/reproduction signal jitter. The control of the position of the recording/reproduction element in the spacing direction can maintain minimum spacing. Since piezoelectric elements are used, it is possible to control the position of the recording/reproduction element in the disc rotation direction and to control the spacing with high rigidity, high speed, and high accuracy. It is possible to control the position of the recording/reproduction element in the disc rotation direction and spacing simultaneously and without interfering with each other.
By providing a piezoelectric element displaced in the rotation direction of a magnetic disc and a piezoelectric element displaced in the track direction, it is possible to control the position of the recording/reproduction element in the disc rotation direction and in the track direction. By controlling the position of the recording/reproduction element in the disc rotation direction, it is possible to reduce recording/reproduction signal jitter. By controlling the position of the recording/reproduction element in the track direction, it is possible to perform track positioning. Since the piezoelectric elements are used, it is possible to perform the position control of the recording/reproduction element in the disc rotation direction and the track positioning control with high rigidity, high speed, and high accuracy. The position control of the recording/reproduction element in the disc rotation direction and the track positioning control can be performed simultaneously and without interfering with each other.
In another embodiment of the invention, the magnetic head includes a piezoelectric actuator at an air flow out end of a floating type magnetic head slider, the piezoelectric actuator having at both its sides a pair of electrodes, one of which is arranged opposite the air flow out end of the magnetic head slider and the other of which has a recording/reproduction element electrically insulated from the electrode.
With this configuration, a piezoelectric actuator is formed on a slider substrate, and a plurality of recording/reproduction elements is formed at a predetermined interval. After this, the slider substrate is divided into rows and chips so as to produce a plurality of magnetic heads.
By providing the piezoelectric actuator displaced in the spacing direction, it is possible to control the position of the recording/reproduction element in the spacing direction.
By providing the piezoelectric actuator displaced in the track direction, it is possible to control the track positioning of the recording/reproduction element.
By providing the piezoelectric actuator displaced in a rotation direction of a magnetic disc, it is possible to control the position of the recording/reproduction element in the rotation direction of the magnetic disc.
In yet another embodiment of the invention, the magnetic head includes a plurality of layered piezoelectric actuators having different displacement directions and arranged at an air flow out end of a floating type magnetic head slider, wherein a first outer electrode of the layered plurality of actuators is arranged opposite the air flow out end of the magnetic head slider and a second outer electrode of the layered plurality of piezoelectric actuators has a recording/reproduction element electrically insulated from the second outer electrode.
With this configuration, it is possible to form a plurality of layered piezoelectric actuators on a slider substrate and to form a plurality of recording/reproduction elements at a predetermined interval, after which the slider substrate is cut into rows and chips so as to produce a plurality of magnetic heads.
By providing a piezoelectric actuator displaced in the spacing direction and a piezoelectric actuator displaced in the track direction, it is possible to perform position control of the recording/reproduction element in the spacing direction and the track positioning control.
By providing piezoelectric actuator displaced in the rotation direction of a magnetic disc and a piezoelectric actuator displaced in the spacing direction, it is possible to perform position control of the recording/reproduction element in the magnetic disc rotation direction and in the spacing direction.
By providing a piezoelectric actuator displaced in the rotation direction of a magnetic disc, a piezoelectric actuator displaced in the spacing direction, and a piezoelectric actuator displaced in the track direction, it is possible to perform position control of the recording/reproduction element in the magnetic disc rotation direction and spacing direction as well as the track positioning.
The magnetic head production method in accordance with one aspect of the present invention comprises steps of: bonding a piezoelectric element thin plate having on both its sides an electrode film, onto a substrate using one of the electrode films as a bonding surface, forming an insulation thin film on the other electrode film of the piezoelectric thin plate, forming a plurality of recording/reproduction elements at a predetermined interval on the insulation thin film, forming an insulation thin film on the recording/reproduction elements, cutting the substrate which is manufactured in the previous steps into rows, each having recording/reproduction elements arranged in a row, polishing that surface of the row substrate having the recording/reproduction elements, forming a plurality of float planes by etching the side surfaces of the row substrate, forming a protection film on the side surfaces of the row substrate, and cutting the row substrate into slider chips.
With this production procedure, it is possible to economically produce a plurality of magnetic heads.
The magnetic disc apparatus production method in accordance with another aspect of the present invention comprises steps of: bonding a magnetic head (slider chip) produced by the aforementioned method, to a gimbal spring, and wiring the recording/reproduction element and the electrodes of the piezoelectric element in the slider chip, to the gimbal spring.
By using the magnetic head produced according to the aforementioned magnetic head production method, it is possible to economically provide a magnetic disc apparatus having high recording density and high mechanical reliability.